This invention relates to lubricating oil compositions having improved viscosity index, dispersency and pour depressant properties. In particular, this invention is directed to lubricating oil compositions containing succinate ester and succinimide derivatives of copolymers of ethylene and an alpha-olefin which are polyfunctional additives in that they act as a shear stable viscosity index improver as well as a pour depressant and sludge dispersant.
Various compositions and polymeric additives are known and have been employed to improve the viscosity index of lubricating oil compositions when added thereto. One such viscosity index improver additive which has proven effective not only as a viscosity index improver but has exhibited a high degree of shear stability is an amorphous copolymer of ethylene and propylene described in U.S. Pat. No. 3,522,180. However, this copolymer as well as other olefinic copolymers while being effective viscosity index improvers do not act to any substantial degree as dispersants and pour depressants in lubricating oil compositions to which they have been added.
A copending application of the assignee herein, filed on Dec. 29, 1976 as Ser. No. 756,040, discloses and claims the succinimide derivative of a copolymer of ethylene and an alpha olefin which is effective as a viscosity index improver and a dispersant in lubricating oils but which does not function as a lubricating oil pour depressant.
It is an object of this invention to provide a polyfunctional lubricating oil additive effective as a shear stable, viscosity index improver as well as a dispersant and a pour depressant.